The invention relates to a method for the transmission of call control parameters for switching over between a speech transmission mode and a data transmission mode between two media gateway controllers, which are used by way of an IP network between two telecommunication terminal devices separated from any medium or bearer connection.
Service providers, in other words companies which, based for example on the transport services of the partial networks (backbones) of the internet, provide their customers or users with switched data communication facilities, are faced in the communications sector primarily with the challenges associated with introducing new fast and efficient services. In this situation, the network infrastructure for connection network operators (carriers) is a significant cost factor whereby cost savings can be achieved by means of successful optimization.
Before dealing with the question as to how a service provider can take advantage of the data signaling for service management solutions, it is however necessary to consider what the customer is expecting of a service provider who is supplying value added facilities and services. At present, the expectation comprises a whole spectrum of integrated services, a simple and uniform accounting process in real time, and also comprehensive access to measurable and recorded standards of service.
In order to nevertheless achieve an optimization of the operating costs in the case of a service provider despite their provision of comprehensive services, steps are now being taken to set up communication connections which perform the connection setup (call) and the medium or bearer setups separately from one another. As a result, it is possible to revert to a relatively low-cost bearer technology for through-connection of the speech/data channel, whilst for example the signaling is handled separately.
If a disconnection (decomposition) of the connection setup and the medium or bearer setup is carried out, a communication is then needed between at least two media gateway controllers which are used during connection setup for data signaling purposes.
The Diagram in FIG. 1 demonstrates how, in the case of such a disconnection of connection setup and bearer setup, the information required for the setup of a communication connection between two telecommunication terminal devices 1, 2 is exchanged between the individual network components. In this situation, an A subscriber requests a call setup to a telecommunication terminal 2 of a B user, by means of a telecommunication terminal 1 which is connected to a first public telephone network (PSTN) 3 with an associated local switching centre (Local Exchange; LE) 5.
This call request results in a connection setup which takes place by means of two media gateway controllers (MGC) 6, 7. In this situation, information is transmitted by means of a corresponding signaling protocol (Common Channel Signaling CCS:ISUP) to a first media gateway controller 6. The latter communicates for its part with a second media gateway controller 7 by way of a BICC CS2/ISUP+ interface via Q.765.5 BAT (Bearer Application Transport). The second media gateway controller 7 thus receives all the service or performance features which are required in order to setup the connection, and transmits this information to a public telephone network 4 in which the terminal device 2 of the B subscriber is located. The transmission takes place in turn by way of a corresponding signaling protocol.
On the basis of the prior art, it is known that by introducing suitable communication between a media gateway controller and the associated media gateway the cost-effective bearer technologies such as IP can be applied to through-connection of the speech/data channel. At the present time, there exists the ITU-T Standard Q.1902.X BICC CS2 (Bearer Independent Call Control Capability Set 2) with a special Service Indicator in the case of the MTP (Message Transfer Part), and Q.765.5 BAT (Bearer Application Transport) which when employing IP-RTP as the bearer technology describes how its usual services are to be provided to the end user in the telecommunication network when there is a disconnection between connection setups and through-connection of the speech/voice channel. In the meantime, IETF has produced RFC 3204 (ISUP MIME Type) which enables the tunnel transport of ISUP messages in SIP messages. Such SIP messages for the purpose of media gateway controller intercommunication are also referred to as SIP-T messages.
A disadvantage that has become apparent in respect of the known solution is the fact that with regard to intercommunication between media gateway controllers themselves information can only be transmitted between the media gateway controllers by way of the BICC CS2/ISUP+ interface via Q.765.5 BAT (Bearer Application Transport). This holds true particularly when a modification of the bearer is required for the data transmission. Thus, in the case of a fax switchover for example, it is not possible at the present time to transfer the information required for this purpose between the media gateway controllers by means of a SIP protocol because the interworking of SIP to BICC is not yet defined in the ITU-T Standards for BICC CS2. The SIP protocol—in contrast to BICC—is suitable not only as a subscriber protocol for voice connections but also for multimedia (voice and data) and will for this reason acquire an increasing significance from the global viewpoint.